U.S. patent number 5,403,227 [Application Number 08/103,932] was granted by the patent office on 1995-04-04 for machine for grinding and polishing terminated fiber optic cables.
This patent grant is currently assigned to The Whitaker Corporation. Invention is credited to Vinod J. Franklin, James D. Kevern.
United States Patent |
5,403,227 |
Franklin , et al. |
April 4, 1995 |
Machine for grinding and polishing terminated fiber optic
cables
Abstract
An automated machine is disclosed for grinding and polishing the
terminated ends of the optical fibers in fiber optic cables. The
machine utilizes abrasive material in strip form. The abrasive
material is moved in a carriage along a linear path while the
carriage is oscillated in a circle within a plane during polishing.
There are three separate carriages operating concurrently, the
first having a relatively course grade of abrasive while the others
have finer grades. Fixtures holding the cables for polishing are
held in fixture supports that are automatically fed toward the
abrasive material during polishing and retracted after polishing is
complete. The fixture engagement mechanism for the first carriage
engages at a slower rate than do the mechanisms of the other
carriages.
Inventors: |
Franklin; Vinod J. (Hershey,
PA), Kevern; James D. (Wellsville, PA) |
Assignee: |
The Whitaker Corporation
(Wilmington, DE)
|
Family
ID: |
22297775 |
Appl.
No.: |
08/103,932 |
Filed: |
August 6, 1993 |
Current U.S.
Class: |
451/168;
451/166 |
Current CPC
Class: |
B24B
19/226 (20130101); G02B 6/3863 (20130101) |
Current International
Class: |
B24B
19/00 (20060101); B24B 19/22 (20060101); G02B
6/38 (20060101); B24B 007/16 () |
Field of
Search: |
;51/62,67,60,59R,59SS,57,357,283R,142,DIG.5,4
;451/166,165,164,162,168,173,489,41,904,304,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rose; Robert A.
Attorney, Agent or Firm: Schuette; June B.
Claims
We claim:
1. An automated machine for grinding and polishing the terminated
ends of optical fibers in fiber optic cables, comprising:
(a) a frame;
(b) a workstation in said frame;
(C) a rectangular strip of abrasive material having a longitudinal
axis, said abrasive material having a flat surface defining a first
plane within said workstation;
(d) a carriage for holding said abrasive material and moving it
along a first path within said plane, said carriage comprising;
a member having a flat surface upon which said abrasive material is
disposed within said first plane, a drive spindle and a supply
spindle in operational engagement with said strip of abrasive
material, wherein both said spindles are journaled for rotation in
said carriage, and means for rotating said drive spindle causing
said strip of abrasive material to move along said first path;
(e) coupling means for coupling said carriage to said frame so that
said carriage undergoes oscillating motion to move said abrasive
material along a second path different from said first path within
said first plane;
(f) drive means for effecting said oscillating motion of said
carriage;
(g) a fixture for holding said fiber optic cables so that the ends
of the optical fibers are in a desired relation to said abrasive
material in said first plane; and
(h) means for securing said fixture in said frame.
2. The machine according to claim 1 wherein said supply spindle is
on one side of said work area and said drive spindle is on the
opposite side of said work area and wherein said abrasive material
moves along said first path in a direction from said supply spindle
through said work area to said drive spindle.
3. The machine according to claim 1 wherein said carriage includes
a pair of spaced parallel plates rigidly attached together and said
member being disposed between said plates, the axes of said
spindles being substantially normal to said plates.
4. The machine according to claim 1 wherein said oscillating motion
is substantially circular motion so that said second path through
which said abrasive material moves is a circular path.
5. The machine according to claim 1 wherein said coupling means
comprises a movable plate to which said carrier means is attached
and a pair of orthogonal oriented slide assemblies for coupling
said movable plate to said frame, and means for moving said movable
plate along said second path.
6. The machine according to claim 5 wherein said means for moving
said movable plate comprises a motor, a drive shaft rotationally
coupled to said motor, and an eccentric coupling between said drive
shaft and said movable plate.
7. The machine according to claim 6 wherein said eccentric coupling
is a crank pin attached to said drive shaft with said pin
projecting therefrom into an opening in said movable plate.
8. The machine according to claim 7 including a gear attached to
said crank pin said gear drivingly coupled to said drive spindle so
that as said gear rotates with said drive shaft said abrasive
material is moved along said first path.
9. The machine according to claim 1 including engagement means for
holding said fixture in a first position away from said abrasive
material and for moving said fixture at a first predetermined rate
toward said abrasive material to a second position adjacent
thereto, so that when said fixture is in said first position said
end of said optical fibers are spaced from said abrasive material
and when said fixture is moving toward said second position said
ends of said optical fibers engage said abrasive material.
10. The machine according to claim 9 wherein said movement along
said first path, said movement along said second path, and said
movement of said fixture are all effected by means of a single
motor.
11. The machine according to claim 9 including a second carriage
similar to said carriage, a sheet of second abrasive material that
is different from said abrasive material and having a flat surface
defining a second plane within said workstation and arranged to
move within said second carriage along a path parallel to said
first path, a second fixture for holding said fiber optic cables so
that the ends of the optical fibers are in a desired relation to
said strip of second abrasive material, and engagement means for
holding said second fixture in a first position away from said
second abrasive material and for moving said second fixture at a
second predetermined rate toward said second abrasive material to a
second position adjacent thereto, so that when said second fixture
is in said first position said end of said optical fibers are
spaced from said second abrasive material and when said fixture is
moving toward said second position said ends of said optical fibers
engage said second abrasive material.
12. The machine according to claim 11 wherein said second
predetermined rate is different than said first predetermined
rate.
13. The machine according to claim 11 wherein said abrasive
material and said second abrasive material are both in strip form
and each of said carriage and said second carriage include a drive
spindle and a supply spindle in operational engagement with its
respective said strip of abrasive material, both of said spindles
in said two carriages being journaled for rotation in their
respective said carriage, including means for rotating each said
drive spindle so that its said strip of abrasive material is caused
to move along said first path.
14. A power tool comprising a housing, a yoke movably mounted on
the housing, the yoke being provided with an enlarged bore, a
ratchet wheel rotatably mounted in said enlarged bore and including
a central aperture which is concentric with the enlarged bore,
power means for driving the yoke in alternating pivotal directions
about said ratchet wheel, a pair of complementary pawls pivotally
mounted in said yoke, each pawl sized for extending into the
enlarged bore and into engagement with the ratchet wheel, biasing
means for urging the pawls toward the ratchet wheel, and pawl
control means disposed in said enlarged bore for selectively
disengaging one of said pawls from contact with the ratchet wheel,
the pawl control means being also provided with a centrally located
aperture which is in coaxial communication with the aperture of the
ratchet wheel whereby an elongated threaded member can be inserted
through the enlarged bore and apertures and a fastener may be
rotatably driven on the member by the power tool.
15. A power tool comprising a housing, a yoke movably mounted on
the housing, the yoke being provided with an enlarged bore, a
ratchet wheel rotatably mounted in said enlarged bore and including
a central aperture which is concentric with the enlarged bore,
power means for driving the yoke in alternating pivotal directions
about said ratchet wheel, a pair of complementary pawls pivotally
mounted in said yoke, each pawl sized for extending into the
enlarged bore and into engagement with the ratchet wheel, biasing
means for urging the pawls toward the ratchet wheel, and pawl
control means disposed in said enlarged bore for selectively
disengaging one of said pawls from contact with the ratchet wheel,
the pawl control means being a control member which is disposed
within and supported for rotation about a central longitudinal axis
of said enlarged bore.
16. In an automated machine for grinding and polishing the
terminated ends of optical fibers in fiber optic cables, having: a
frame; a workstation in said frame; an abrasive material having a
flat surface defining a first plane within said workstation;
carrier means for holding said abrasive material and moving it
along a first path within said plane; coupling means for coupling
said carrier to said frame so that said carrier undergoes
oscillating motion to move said abrasive material along an second
path within said first plane; drive means for effecting said
oscillating motion of said carrier; a fixture for holding said
fiber optic cables so that the ends of the optical fibers are in a
desired relation to said abrasive material in said first plane; and
means for securing said fixture in said frame,
an engagement mechanism for holding said fixture in a first
position away from said abrasive material and for moving said
fixture at a predetermined rate toward said abrasive material to a
second position adjacent thereto, so that when said fixture is in
said first position said end of said optical fibers are spaced from
said abrasive material and when said fixture is moving toward said
second position said ends of said optical fibers engage said
abrasive material.
17. The machine according to claim 16 where said engagement
mechanism comprises:
(a) a slide having a stationary portion attached to said frame and
a movable portion to which is removably mounted said fixture;
(b) a lead screw and nut assembly, said lead screw journaled for
rotation in said frame and said nut attached to said movable
portion of said slide;
(c) a motor;
(d) coupling means for drivingly coupling said motor to said lead
screw so that said lead screw can be rotated in one direction to
advance said fixture toward said second position at a predetermined
rate, and in an opposite direction to retract said fixture to said
first position.
18. The machine according to claim 17 wherein said coupling means
includes a slip clutch and stop means for limiting rotation of said
lead screw in both said directions thereby defining said first and
second positions.
19. The machine according to claim 18 wherein said stop means
comprises a spindle rotationally coupled to said slip clutch, a
gear attached to said spindle and drivingly coupled to said lead
screw, a member attached to said spindle that rotates therewith,
and a stop attached to said frame so that when said fixture is in
said first position said member is in abutting engagement with one
side of said stop and when said fixture is in said second position
said member is in abutting engagement with the other side of said
stop.
20. The machine according to claim 16 wherein said grinding and
polishing includes removal of material from said ends of said
optical fibers at a specific rate, and wherein said predetermined
rate of movement of said fixture toward said abrasive material is
equal to or less than said specific rate.
Description
FIELD OF THE INVENTION
The present invention relates to a machine for grinding and
polishing the terminated ends of optical fibers in fiber optic
cables.
BACKGROUND OF THE INVENTION
Polishing machines for grinding and polishing the ends of fiber
optic cables are usually of the type having a rotating abrasive
disk that is maintained relatively flat. The optical fiber is
secured in a fixture having a flat bottom. The end of the optical
fiber that is to be polished projects slightly below this bottom
surface, sometimes under the urging of a spring mechanism to
control the forces on the fragile optical fiber. The fixture, with
its fiber optic cable attached, is carefully lowered onto the
rotating abrasive disk and made to undergo a standard polishing
pattern such as circular or figure eight. The polishing usually
occurs in a particular segment of the rotating disk so that, as
polishing continues, the same abrasive surface is continually
presented to the tips being polished. There are usually three or
more stages of polishing that must be done in sequence, from
relatively course abrasive to very fine. Prior to machine
polishing, however, it is usually necessary to hand polish the tips
to remove the protruding fiber stubs to prevent damage. In certain
prior art polishing machines, during the final stage the bottom
surface of the fixture contacts the abrasive disk so that the end
of the optical fiber is polished to a flat surface flush with the
bottom surface of the fixture. Other prior art polishing machines
rely upon the tips of the optical fibers themselves in contact with
the abrasive surface to maintain the axes of the fixture and the
cables somewhat perpendicular to the surface of the abrasive
material. In these machines the fixture itself does not contact the
abrasive material, therefore, the quality of the final polished
surfaces of the cable is dependant upon the amount of ferrule
projection below the bottom of the fixture. Such projections will
vary due to variations in the manufacturing of the terminated
cables. That is, when the cables are loaded into the fixture they
are positioned with respect to some feature of the connector such
as a shoulder. This results in the tips of the optical fibers
extending below the bottom surface of the fixture by varying
amounts, the three tips that extend the farthest being the ones
that establish the initial angle between the axes and the abrasive
surface. With such an arrangement some of the optical fibers are
polished more than others resulting in inconsistency and varying
quality.
What is needed is a polishing machine that controls the relative
motion of the tips of the optical fibers with respect to the
abrasive material so that fresh abrasive is always presented to the
tips for efficient and high quality polishing. To eliminate the
need for preparatory hand polishing, the machine should allow for
relatively slow engagement during the initial stage of polishing
with a more normal rapid engagement during later stages.
Additionally, the tips of the optical fibers should be located in a
plane that is parallel with the abrasive surface prior to polishing
and the fixture that holds the fiber optic cables should be
maintained in this plane during polishing, thereby obviating the
alignment and quality problems mentioned above or the need for the
fixture to contact the abrasive material to maintain vertical
alignment.
SUMMARY OF THE INVENTION
An automated machine is disclosed for grinding and polishing the
terminated ends of optical fibers in fiber optic cables. The
machine includes a frame, a workstation in the frame, and an
abrasive material having a flat surface defining a first plane
within the workstation. A carrier means is provided for holding the
abrasive material and moving it along a first path within the
plane. Coupling means is provided for coupling the carrier to the
frame so that the carrier undergoes oscillating motion to move the
abrasive material along an arcuate second path within the first
plane. A drive means effects the oscillating motion of the carrier.
A fixture for holding the fiber optic cables is arranged so that
the ends of the optical fibers are in a desired relation to the
abrasive material in the first plane, including means for securing
the fixture in the frame.
DESCRIPTION OF THE FIGURES
FIG. 1 is a front view a polishing machine incorporating the
teachings of the present invention;
FIG. 2 is a side view of the machine shown in FIG. 1;
FIG. 3 is a top view of the machine shown in FIG. 1;
FIG. 4 is a partial cross-sectional view taken along the lines 4--4
in FIG. 3;
FIG. 5 is a view similar to that of FIG. 4 with the orthogonal
slide assembly removed;
FIG. 6 is a cross-sectional view taken along the lines 6--6 of FIG.
3;
FIG. 7 is a partial top view of a portion of one of the carriages
taken along the lines 7--7 in FIG. 6;
FIG. 8 is a partial cross-sectional view taken along the lines 8--8
in FIG. 5;
FIG. 9 is a partial cross-sectional view taken along the lines 9--9
in FIG. 5; and
FIG. 10 is a partial cross-sectional view taken along the lines
10--10 in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
There is shown in FIGS. 1, 2, and 3 a grinding and polishing
machine 10 having a workstation 11 for finishing the terminated
ends of fiber optic cables. The machine includes a frame consisting
of a base plate 12 and a U-shaped support 14 secured to the base
plate by four screws 16. The base plate 12 is mounted to a suitable
table 18 to position the machine for convenient operator access. As
shown in FIG. 4 a rectangular carriage plate 20 is coupled to the
base plate 12 with an orthogonal slide assembly 22 therebetween.
The slide assembly consists of three rectangular shaped, open
center, members 24 separated by two pairs of slides 26 and 28 which
are attached to the members 24 by any suitable means. The upper
most member 24 is attached to the bottom of the carriage plate 20
by the screw fasteners 30 and the lower most member 24 is attached
to the base plate 12 by screw fasteners 32, which are threaded into
the base plate. A pair of spacer blocks 34 are disposed between the
lower most member 24 and the base plate 12, as best seen in FIG. 4.
The pair of slides 26 allow movement in one direction while the
pair of slides 28 allow movement in a transverse direction. This
allows the carriage plate 20 to move in any direction within a
plane that is parallel to the base plate 12. As shown in FIG. 5, a
drive shaft 40, vertically disposed with respect to the base plate
12, is coupled to the carriage plate 20 by means of an eccentric
crank 42 having a shaft 44 extending from the crank along an axis
that is parallel to, but offset from the axis of the drive shaft.
The shaft 44 extends into a slip fit bushing 46 that is pressed
into a hole in the carriage plate 20. The drive shaft is journaled
for rotation in two ball bearings 48, one of which is in a
counterbore in the base plate 12 and the other of which is in a
bearing support plate 50. The plate 50 is positioned on a pair of
spacer blocks 52 and attached to the base plate 12 with the screws
54. A sprocket wheel 56 is attached to the drive shaft 40 and is
interconnected to a source of rotational power as will be described
below. The sprocket 56 includes a one way clutch, not shown, that
allows rotational power to be transmitted in only one direction,
for a purpose that will be explained below. A gear 58 is rigidly
attached to and rotates with the shaft 44 for a purpose that will
be explained below.
Three carriages 60, 62, and 64 are shown in FIGS. 1, 2, and 3 for
carrying abrasive material of various grit sizes, in strip form.
The carriage 60 carries a relatively coarse material 66 while the
other two carriages 62 and 64 carry medium and fine grit materials
68 and 70 respectively. The carriages 60, 62, 64 are substantially
identical, each consisting of a supply carriage 72, a take-up
carriage 76, and a workstation platen 74 therebetween. The supply
carriage has two side plates 78 spaced apart by two spacer blocks
80 at one end and a mounting plate 82 at the other end, as best
seen in FIG. 6 The side plates 78 are attached to the spacer blocks
and the mounting plate by means of screws threaded into the edges
of the blocks and the plate. The mounting plate 82 is rigidly
attached to the carriage plate 20 by means of the screws 84. The
take-up carriage, being of similar structure, has two side plates
86 spaced apart by several spacer rods 88 and a mounting plate 82,
which also is rigidly attached to the carriage plate by means of
the screws 84. The two side plates 86 are secured to the spacer
rods by means of screws threaded into the rods. All three of the
carriages 60, 62, and 64 are attached to the carriage plate 20 in
this manner resulting in a rigid assembly. The supply carriage
includes a supply spindle 88 containing a roll of abrasive material
90 in strip form, an idler spindle 92 about which the abrasive
material is passed, and a spindle 94 having a slip clutch 96. A
belt 98 and sprockets couple the spindles 92 and 94 together so
that a drag is created as the strip of abrasive material is pulled
in the direction of the arrow 100, shown in FIG. 6. The take-up
carriage includes a take-up spindle 102 for receiving and winding
up the strip 90 of abrasive material after use, and a horizontally
disposed shaft 104 journaled for rotation in the side plates 86.
The shaft 104 extends through all three of the carriages 60, 62,
and 64. Three sprockets 106 are arranged along the shaft 104 in
alignment with similar sprockets attached to each of the take-up
spindles 102. Three belts 108 interconnect these pairs of sprockets
so that all of the take-up spindles are rotationally coupled to the
shaft 104.
A shaft 114 extends horizontally through the three carriages 60,
62, and 64 and is journaled for rotation in a bracket 111 that is
secured to the carriage plate 20 by screws 113. A pinch roller 110
is secured to the shaft 114 and a mating pinch roller 108 is in
operational engagement therewith and is journaled for rotation in
the bracket 111. A guide roller 112 is also journaled for rotation
in the bracket 111. A similar bracket, pinch rollers, and guide
roller are provided in alignment with each of the carriages 60, 62,
and 64. The platen 74 is secured on a bracket 120 which is attached
to the carriage plate 20 by screws 122. As is shown in FIG. 6, the
strip 90 of abrasive material is threaded over the idler roller 92,
over the platen 74, the guide roller 112, down around the driven
pinch roller 110, and in between the two pinch rollers 110 and 108,
then to the take-up spindle 102. The strip 90 of abrasive material
is held firmly against the platen 74 by tension in the strip due to
the affect of the drag of the slip clutch 96 while the pinch
rollers are advancing the strip across the platen. The area of the
strip 90 in contact with the platen, being a work area, defines a
plane 124 within which the grinding and polishing takes place, and
will be discussed further below. Since the abrasive material passes
through the work area prior to engagement with the pinch rollers
there is no possibility that abrasive material, damaged or
contaminated by the pinch rollers, could adversely affect the
quality of the polished cable end. The surface of the platen 74 may
have some resiliency to soften the contact somewhat between the
fragile tips of the optical fibers and the abrasive material during
polishing. The surface resiliency of the platens in the three
carriages 60, 62, and 64 may be different depending on the
characteristics of the particular abrasive material being used in
each and the type of fiber optic cable being finished.
There is shown in FIGS. 8 and 9 the drive mechanism for the shafts
104 and 114 which advance the strip 90 of abrasive material. A
bearing support plate 130 is spaced from the carriage plate 20 and
rigidly attached thereto by spacer blocks 132, as best seen in FIG.
5. There are four shafts journaled for rotation in the bearing
plate 130 and the carriage plate 20 by means of eight bearings, as
shown. Note that these shafts are shown slightly out of position
for clarity. They are a drive shaft 134, a pinch roller shaft 136,
a gear reduction shaft 138, and a take-up drive shaft 140. The
drive shaft 134 has a gear 139 attached thereto in mating
engagement with the gear 58 and two sprockets 142 and 144. The
take-up drive shaft 140 has a sprocket 146 attached thereto and is
driven by a belt 148 that is in driven engagement with the sprocket
144. Similarly, the gear reduction shaft 138 has a sprocket 150
attached thereto and is driven by a belt 152 that is in driven
engagement with the sprocket 142. The pinch roller shaft 136 and
the gear reduction shaft 138 each have mating gears 154 and 156
attach thereto respectively. A worm gear 158 is formed on the end
of the shaft 136 and is in driving engagement with a mating worm
gear formed in the shaft 114. The gear 156 is smaller than the gear
154 to provide the desired gear ratio to the shaft 114. The take-up
drive shaft 140 extends above the carriage plate 20 and has a bevel
gear 158 attached thereto. The shaft 104 has a bevel gear 160 in
mating engagement with the bevel gear 158 for driving the shaft
104. It will be appreciated that as the crank 42 is rotated, the
crank pin 44 also rotates carrying along with it the gear 58. This
then drives the shaft 134 which in turn drives the shafts 136 and
140.
As is shown in FIGS. 1, 2, 3, and 6, the U-shaped support 14
includes a horizontal bar 15 that extends over the three carriages
60, 62, and 64 and carries the engagement mechanisms 170, 172, and
174 that support and move the cable holding fixtures toward and
away from the abrasive material in the work station. Each
engagement mechanism is vertically over its respective carriage in
position for moving the tips of fiber optic cables into polishing
engagement with the respective strips of abrasive material. The
three engagement mechanisms are substantially identical in
construction, except that the mechanism 170 moves at a slower rate
than do the other two mechanisms, for a purpose that will be set
forth below. The engagement mechanism 174 will be described in
detail here. It will be understood that each of the three
engagement mechanisms have similar structures. As shown in FIG. 6,
the mechanism 174 includes a slide 176 having its stationary member
attached to the bar 15 and a fixture support 178 attached to the
movable member of the slide. The fixture support 178 includes a
dovetail for receiving a mating tenon of a cable holding fixture
180, as best seen in FIG. 6 and includes a locking lever 179, as
best seen in FIG. 3, that securely locks the fixture to the fixture
support. The fixture 180 is arranged to accurately position and
hold a plurality of fiber optic cables so that the tips of their
optical fibers are in a common plane that is coplanar with the
plane 124. Such a fixture is disclosed in copending patent
application Ser. No. 08/088,711, filed Jul. 8, 1993, and having
attorney docket number 15629, which is incorporated herein by
reference. A lead screw 182 is arranged parallel to the dovetail
and is journaled for rotation in a bracket 184 attached to the bar
15. The lead screw 182 is in threaded engagement with a nut
attached to the fixture support 178 so that as the lead screw is
rotated in one direction the fixture support is advanced toward the
platen 74 and when rotated in the other direction the fixture
support is withdrawn away therefrom. A sprocket 186 is attached to
the top end of the lead screw 182 and is driven by a belt 188 that
couples the sprocket 186 to a drive sprocket 190.
As best seen in FIG. 10, the sprocket 190 is attached to a shaft
192 that is journaled in bearings 194 pressed into bores formed in
the upper and lower surfaces of the bar 15. A second shaft 196 is
disposed in a larger bore 198 formed through the bar 15, adjacent
the shaft 192. The shaft 196 includes a slip clutch 197 that will
slip at a preset torque allowing one end to rotate freely while the
other end remains stationary. The bore 198 is closed at each end by
a bushing 200 that is held in place by a set screw threaded into
the wall of the bar 15. The shaft 196 is journaled in bearings 202
which are pressed into holes formed in the bushings 200. A gear 204
is attached to the shaft 196 and is in mating engagement with a
gear 206 that is attached to the shaft 192 so that as the shaft 196
is rotated the shaft 192 also rotates as well as does the lead
screw 182. A disk 210 having a pin 212 extending upwardly therefrom
is rigidly attached to the end of the shaft 196 above the bar 15. A
stop bar 214 is attached to the top surface of the bar 15, as shown
in FIG. 10, and is arranged to abut the pin 212 when the disk 210
is rotated far enough in either direction, thereby limiting the
rotation of the gear 204 to less than one full turn. By choosing
the gear ratio of the two gears 204 and 206, any desired velocity
of movement of the fixture 180 toward the platen 74 can be
achieved. By varying the thickness of the stop bar 214, the amount
of rotation of the disk 210 can be controlled and thereby the exact
position of the fixture 180, relative to the platen 174, can be
adjusted. A horizontal drive shaft 220 extends along the lower
surface of the bar 15 over the three carriages 60, 62, and 64. The
shaft 220 is journaled for rotation in bearings 222 that are
pressed into blocks 224 that in turn are attached to the bar 15 by
suitable screw fasteners. A collar 226 is secured to each end of
the shaft 220 to control end play. A bevel gear 228 is attached to
the shaft 220 in driving engagement with a mating bevel gear 230
attached to the shaft 196. As shown in FIG. 10, a shaft 232 is
disposed in a bore 234 formed through the bar 15 near the left most
end thereof. The shaft 232 includes a slip clutch 197 and is
journaled in bearings 202 that are pressed into bushings 200 and
held in the bore 234 by set screws in a manner similar to that of
the shaft 196. The shaft 232 has a bevel gear 236 attached to the
end thereof in driving engagement with a mating bevel gear 238
attached to the shaft 220. A sprocket 240 is attached to the top of
the shaft 232 above the bar 15, as viewed in FIG. 10. As best seen
in FIGS. 1, 2, and 3, a motor 250 is mounted on a bracket 252 which
is rigidly attached to the base plate 12. A bevel gear 254 attached
to the output shaft of the motor is in driving engagement with a
bevel gear 256 attached to a vertically disposed shaft 258. The
shaft 258 is journaled in bearings in the end flanges of the
bracket 252. A sprocket 260 is attached to an end of the shaft 258
that extends above the top surface of the bar 15 so that the
sprocket 260 is in alignment with the sprocket 240. A drive belt
262 rotationally couples the two sprockets 240 and 260. An idler
sprocket 264 and associated shaft and bearings are provided for
adjustment. A sprocket 264 is attached to the lower end of the
shaft 258 in alignment with the sprocket 56 on the shaft 40 shown
in FIG. 5. A belt 266 drivingly couples the shaft 258 to the shaft
40. This arrangement provides the necessary circular movement of
the carriage plate 20, the linear movement of the strip 90 of
abrasive material, and the movement of the fixtures 180 toward and
away from the abrasive material, by means of the single motor 250.
An on-off switch 266 is arranged on the table 18 in a convenient
location. The switch 266 signals a programmable controller 274,
that is attached to the under side of the table 18, to initiate the
polishing cycle.
In operation, fixture having fiber optic cables to be polished is
loaded into the fixture support 178 of the carriage 60 and the
locking handle 179 closed to lock the fixture in place. The switch
266 is actuated and the programmable controller begins the
polishing cycle by starting the motor 250. As rotational power is
transmitted throughout the system the carriage plate and the
attached three carriages 60, 62, and 64 begin to oscillate so that
the surface of the strip 90 of abrasive material in direct
engagement with the platen 74 undergoes circular motion in the
plane 124. Simultaneously, the pinch rollers 108 and 110 advance
the strip 90 from left to right toward the take-up spindle 102, as
viewed in FIG. 6. Simultaneously, the lead screw 182 is rotated by
the engagement mechanism 170 at a desired slow rate, as established
by the ratio of the two gears 204 and 206 as set forth above. As
rotation of the lead screw 182 continues, the tips of the optical
fibers of the cables held in the fixture begin to engage the strip
90 of abrasive material at this relatively slow rate and are ground
smooth. The rate of feed of the tips of the optical fibers toward
the abrasive material is chosen to be less than the rate of removal
of material from the grinding process so that any protruding fiber
stubs will be ground down without damage to either the abrasive
material or the optical fiber. This eliminates the need for hand
preparation. The slow rate of engagement prevents over stressing
the optical fibers. As the fixture continues to advance toward the
platen 74, the tips are ground to a common length. As this occurs
the pin 212 of the rotating disk 210 engages the stop bar 214
thereby stopping rotation of the gear 214 and halting the movement
of the fixture toward the abrasive material. At this point the slip
clutch 197 allows the shaft 220 to continue rotating. While the
motor 250 continues to run, the fixture 180 is held in this
position for a specific time to allow adequate time for the
grinding to be complete. As shown in FIG. 7, the combination of the
circular motion, shown in phantom lines at 268, of the carriage
plate 20 and the linear motion of the strip 90 of abrasive material
through the carriage produces a helical path of contact 270 of the
tip 272 of the optical fiber with the surface of the strip 90. The
phantom lines on either side of the strip 90, shown in FIG. 7,
represent the lateral limits of movement of the strip during
oscillation of the carriage plate 20. Note that the tip is
continually exposed to fresh abrasive as the operation continues.
At the end of this time period the direction of the motor 250 is
automatically reversed by the programmable controller 274 causing
the power distribution shafts to also reverse direction. Because
the sprocket 56 includes a one way clutch in its structure, it
simply rotates in the opposite direction without transmitting power
to the shaft 44, therefore, the oscillating motion of the carriage
plate 20 and the linear motion of the strip 90 of abrasive material
cease. However, the shaft 220 is now rotating in the opposite
direction causing the engagement mechanism 174 to lift the fixture
180 away from the strip 90 of abrasive material. Such rotation
continues until the pin 212 of the rotating disk 210 engages the
opposite side of the stop bar 214, at which time the slip clutch
197 again begins to slip. The fixture 180 is now in its withdrawn
position and the electrical power to the motor 250 is cut off by
the programmable controller 274. The fixture 180 is then
transferred from the fixture support in the carriage 60 to the
fixture support in the carriage 62 and the process repeated.
However, since the tips of the optical fibers in the fixture are
now substantially flush with their ferules the engagement mechanism
174 of the carriage 62 may move the tips into engagement with the
abrasive material at a faster rate. This is accomplished by a
different ratio between the gears 204 and 206. Similarly, the ratio
of these gears in the engagement mechanism of the carriage 64 is
set for the faster rate.
An important advantage of the present invention is that the strip
of abrasive material is moved, with respect to the tips of the
ferrules, in both a circular path and a linear path so that the
tips being polished are always moving over fresh abrasive material.
There is no possibility that abrasive material, damaged or
contaminated by the pinch rollers, could adversely affect the
quality of the polishing operation. Additionally, the engagement
mechanism of the first carriage has a much slower rate of
engagement than the others to assure that the optical fibers in
this first stage of grinding will be ground down without being over
stressed or damaged by the grinding process. This eliminates the
need for initial hand preparation to remove fiber stubs. The unique
arrangement of the distribution of rotational power permits the use
of only one motor for effecting the oscillating motion of the
carriage plate, the linear motion of the strip of abrasive
material, and the motion of the fixture engagement mechanism,
resulting in significant cost savings to manufacture and to operate
and maintain the machine.
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